/*
 *-------------------------------------------------------------------
 *
 * ALPN Callback for Servers --
 *
 *	Perform server-side protocol (http/1.1, h2, h3, etc.) selection for the
 *	incoming connection. Called after Hello and server callbacks
 *	Where 'out' is selected protocol and 'in' is the peer advertised list.
 *
 * Results:
 *	None
 *
 * Side effects:
 *	Calls callback (if defined)
 *

    State *statePtr = (State*)arg;
    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;
    int code, res;

    dprintf("Called");

    if (statePtr->callback == (Tcl_Obj*)NULL) {
	return SSL_TLSEXT_ERR_OK;
    } else if (ssl == NULL) {
    if (ssl == NULL || arg == NULL) {
	return SSL_TLSEXT_ERR_NOACK;
    }

    /* Select protocol */
    if (SSL_select_next_proto(out, outlen, statePtr->protos, statePtr->protos_len,
	in, inlen) == OPENSSL_NPN_NEGOTIATED) {
	res = SSL_TLSEXT_ERR_OK;
    } else {
	/* No overlap, so first client protocol used */
	/* No overlap, so use first client protocol */
	res = SSL_TLSEXT_ERR_NOACK;
    }

    if (statePtr->callback == (Tcl_Obj*)NULL) {
	return SSL_TLSEXT_ERR_OK;
    }

    cmdPtr = Tcl_DuplicateObj(statePtr->callback);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("alpn", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(*out, -1));

    Tcl_Preserve((ClientData) interp);
    Tcl_Preserve((ClientData) statePtr);

    Tcl_Interp *interp	= statePtr->interp;
    Tcl_Obj *cmdPtr;
    int code;
    char *servername = NULL;

    dprintf("Called");

    if (statePtr->callback == (Tcl_Obj*)NULL) {
	return SSL_TLSEXT_ERR_OK;
    } else if (ssl == NULL) {
    if (ssl == NULL || arg == NULL) {
	return SSL_TLSEXT_ERR_NOACK;
    }

    servername = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
    if (!servername || servername[0] == '\0') {
        return SSL_TLSEXT_ERR_NOACK;
    }

    if (statePtr->callback == (Tcl_Obj*)NULL) {
	return SSL_TLSEXT_ERR_OK;
    }

    cmdPtr = Tcl_DuplicateObj(statePtr->callback);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("sni", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(servername , -1));

    Tcl_Preserve((ClientData) interp);
    Tcl_Preserve((ClientData) statePtr);

    const unsigned char *p;
    size_t len, remaining;

    dprintf("Called");

    if (statePtr->callback == (Tcl_Obj*)NULL) {
	return SSL_CLIENT_HELLO_SUCCESS;
    } else if (ssl == NULL) {
    } else if (ssl == NULL || arg == NULL) {
	return SSL_CLIENT_HELLO_ERROR;
    }

    /* Get names */
    if (!SSL_client_hello_get0_ext(ssl, TLSEXT_TYPE_server_name, &p, &remaining) || remaining <= 2) {
        return SSL_CLIENT_HELLO_ERROR;
    }

    /* Create Tcl_Channel BIO Handler */
    statePtr->p_bio	= BIO_new_tcl(statePtr, BIO_NOCLOSE);
    statePtr->bio	= BIO_new(BIO_f_ssl());

    if (server) {
	/* Server callbacks */
	SSL_CTX_set_alpn_select_cb(statePtr->ctx, ALPNCallback, (void *)statePtr);
	SSL_CTX_set_tlsext_servername_arg(statePtr->ctx, (void *)statePtr);
	SSL_CTX_set_tlsext_servername_callback(statePtr->ctx, SNICallback);
	SSL_CTX_set_client_hello_cb(statePtr->ctx, HelloCallback, (void *)statePtr);
	if (statePtr->protos != NULL) {
	    SSL_CTX_set_alpn_select_cb(statePtr->ctx, ALPNCallback, (void *)statePtr);
	}

	/* Enable server to send cert request after handshake (TLS 1.3 only) */
	if (request && post_handshake) {
	    SSL_verify_client_post_handshake(statePtr->ssl);
	}

	statePtr->flags |= TLS_TCL_SERVER;

	SSL_CTX_set_options(ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
    }

    SSL_CTX_set_app_data(ctx, (void*)interp);	/* remember the interpreter */
    SSL_CTX_set_options(ctx, SSL_OP_ALL);	/* all SSL bug workarounds */
    SSL_CTX_set_options(ctx, off);		/* disable protocol versions */
#if OPENSSL_VERSION_NUMBER < 0x10101000L
    SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);	/* handle new handshakes in background */
    SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY);	/* handle new handshakes in background. On by default in OpenSSL 1.1.1. */
#endif
    SSL_CTX_sess_set_cache_size(ctx, 128);

    /* Set user defined ciphers, cipher suites, and security level */
    if ((ciphers != NULL) && !SSL_CTX_set_cipher_list(ctx, ciphers)) {
	    Tcl_AppendResult(interp, "Set ciphers failed: No valid ciphers", (char *) NULL);
	    SSL_CTX_free(ctx);